The research program is designed to provide information on basic aspects of neutron capture therapy. This information will form the basis for application of NCT to therapy of many diseases. The program has four parts. Part 1 consists of a study of track etch autoradiography used to determine the distribution of boron compounds on a cellular level in biological tissue. The technique will be used with scanning and transmission electron microscopy. Part 2 consists of a study using track etch autoradiography to determine the biodistribution of new boron labeled compounds on a macroscopic basis. Part 3 is a study on the possible use of nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) to determine the distribution of 10B or 11B in vivo and to provide quantitative data for dosimetry. Part 4 is an analysis of accelerator produced epithermal neutron sources suitable for use in a hospital environment. The availability of epithermal neutrons may permit NCT to be employed in brain and in other organs without surgery. Fractionated therapy may then be possible.